This application claims benefit of Korean patent application number P2000-08667, filed Feb. 23, 2000, which is hereby incorporated by reference for all purposes as if fully set forth herein.
This invention relates to a liquid crystal display having a tape carrier package including a mounted integrated circuit, and more particularly to a tape carrier package with dummy pads that are capable of fortifying a bonding force in bonding the tape carrier package onto a liquid crystal panel. Also, the present invention is related to a method of fabricating a liquid crystal display with dummy pads that are capable of fortifying a bonding force between the tape carrier package and the liquid crystal panel.
Generally, an active matrix liquid crystal display uses thin film transistors (TFTs) as switching devices to display a natural-looking moving picture. Since such a liquid crystal display can be made into a smaller-size device than a cathode ray tube, it is commercially viable for use as a monitor such as a portable television, lap-top personal computer or other consumer device.
The active matrix liquid crystal display displays a picture corresponding to video signals such as television signals on a pixel (or picture element) matrix having pixels arranged at each intersection between gate lines and data lines. Each pixel includes a liquid crystal cell for controlling a transmitted light quantity in accordance with a voltage level of a data signal from a data line. A TFT (thin film transistor) is installed at an intersection between a gate line and a data line to switch a data signal to be transferred to the liquid crystal cell in response to a scanning signal (i.e., a gate pulse) from the gate line.
Such a liquid crystal display requires a number of integrated circuits (ICs) connected to the data lines and the gate lines to apply data signals and scanning signals to the data lines and the gate lines, respectively. The ICs are installed between the print wiring board (PWB) and the liquid crystal panel to apply signals supplied from the PWB to the data lines and the gate lines. IC mounting methods include chip on board, hereinafter referred to as xe2x80x9cCOBxe2x80x9d, tape automated bonding, hereinafter referred to as xe2x80x9cTABxe2x80x9d, and chip on glass, hereinafter referred to as xe2x80x9cCOGxe2x80x9d. (Other methods are also possible.) The COB system is ainly used for a monochromatic liquid crystal display having a pixel pitch of more than 300 xcexcm. As shown in FIG. 1, in this COB system, ICs 8 are mounted on a PWB 6 and a heat-seal connector 10 connects the PWB 6 and a glass substrate 3 in a liquid crystal panel 2. In this case, a back light unit 4 used as a light source is provided between the liquid crystal panel 2 and the PWB 6. As shown in FIG. 2, in the TAB system, ICs 14 are mounted on a tape carrier package (TCP) 12. The TCP 12 is connected between the PWB 6 and the liquid crystal panel 3. As shown in FIG. 3, in the COG system, an IC chip 20 is directly mounted on a glass substrate 17 in a liquid crystal panel 16.
The above mentioned TAB IC mounting method has been widely employed because it can widen an effective area of the panel and has a relatively simple mounting process.
As shown in FIG. 4, the TCP 12 employed in the TAB system includes a base film 22 on which is mounted an IC 14. The base film 22 is also provided with input and output pads 24 and 26 connected to input and output pins of the ICs 14. The input and output pads 24 and 26 have a two-layer structure in which copper(Cu) is plated with tin(Sn) for preventing an oxidation. Line widths of the input pads 24 are set to be larger than those of the output pads 26. As shown in FIG. 5, the input pads 24 of the base film 22 are connected, via an anisotropic conductive film (ACF) 30, to pads 28 on the PWB 6. The output pads 26 are also connected via the ACF 30 to pads 28 on the liquid crystal panel 2.
Recently, in order to fortify a bonding force between the liquid crystal panel and the TCP 42, separate dummy pads 50 and 52 have been provided at a liquid crystal panel 44 and a TCP 42 as shown in FIG. 6. The dummy pads 50 and 52 function to increase a bonding force between the TCP 42 and the liquid crystal panel 44 by widening a bonded area without being connected to a signal wiring. The dummy pads 50 and 52 are bonded to each other with the ACF 30 therebetween upon bonding the output pads 46 of the TCP 42 to the gate/data pads 48 of the liquid crystal panel 44. Line widths of the dummy pads 52 and 54 are set to be equal to those of the output pads 46 of the TCP 42 and the gate/data pads 48 of the liquid crystal panel 44. Accordingly, the bonding forces of each dummy pad 50 and 52 are the same.
However, the TCP 42 and the liquid crystal panel 44 having the conventional dummy pads have a problem in that, since the bonding forces of each dummy pad 50 and 52 are same, a bonding force generated by the dummy pads 50 and 52 is not satisfactory. As a result, in the liquid crystal display with the conventional dummy pads, the TCP 42 can be separated from the liquid crystal panel 44 due to an impact force applied from the exterior thereof in the course of its fabrication process or its usage. The conventional TCPs 12 and 42 have limited usefulness because of such weak bonding force.
Accordingly, it is an object of the present invention to provide a liquid crystal display having dummy pads with an increased bonding force between a tape carrier package and a liquid crystal panel.
A further object of the present invention is to provide a method of fabricating a liquid crystal display having dummy pads that with an increased bonding force between a tape carrier package and a liquid crystal panel.
In order to achieve these and other objects of the invention, a liquid crystal display with dummy pads according to one aspect of the present invention includes a tape carrier package including first and second dummy pads to which signals are not applied, the first dummy pad having a larger width than the second dummy pad; and a liquid crystal panel including third and fourth dummy pads corresponding to the first and second dummy pads, respectively.
A liquid crystal display with dummy pads according to another aspect of the present invention includes a tape carrier package including output pads for outputting signals from an integrated circuit and dummy pads to which signals are not applied, at least one of said dummy pads having a width different from the output pads; and a liquid crystal panel including dummy pads corresponding to said dummy pads.
A method of fabricating a liquid crystal display with dummy pads according to still another aspect of the present invention includes the steps of forming first and second dummy pads on the tape carrier package in such a manner that the first dummy pad has a width different from the second dummy pad; forming third and fourth dummy pads corresponding to the first and second dummy pads, respectively, on the liquid crystal panel; and bonding the tape carrier package on the liquid crystal panel in such a manner that the first and second dummy pads correspond to the third and fourth dummy pads, respectively.